There's not really anything builtin. You can create a very basic package with the files you have in which you can open regedit to export the registry keys you're interested in.
Alternatelively have a look at vregtool, it can export registry keys from a .tvr. Of course you'll need one of those first. It's created in the sandbox as the thinapp starts, but if it doesn't, well...SOL, I guess.
If the registry keys are only set in a single (or few) branch(es) you can start the virtual regedit (if it starts...) and export the keys from there.
If there are multiple branches used you could consider to make a change in the HKEY_LOCAL_MACHINE.txt and replace all "HKEY_LOCAL_MACHINE\Software" entries with "HKEY_LOCAL_MACHINE\Software\Blablabla". Then build your package (make sure you create regedit.exe) and export the keys from the virtual regedit. In the exported "reg" file rename the keys back (find & replace) to the original value.